How do I reclaim 36 GB of missing space on my iPhone?

Solution 1:

You said you don't want to wipe the phone and reset it, but what about restoring it from a backup? During an iCloud restore, iOS re-downloads most of what it needs from Apple’s servers, so the process might reclaim your lost space, since iOS wouldn’t assign it to anything that isn't actually using it. After the restore, your phone would be returned to the same state you left it in.